Polaris FST IQ Cruiser Owner's Manual page 71

THE PERFECT FIT
FAST M-10 Rear Suspension Adjustments
Static Sag and Ride Height Settings
Rear Spring Preload
If FRA position alone does not allow the setup of the proper amount of
sag, the center retainer of the rear track shock can be replaced with
optional retainers to adjust the preload and change the sag. See your
Polaris dealer for assistance.
Retainer Insert
Part Number
5436109
NOTE:
Whenever ordering any of the retainers listed in the chart, always
order the retainer insert as well. The insert is not removable once
installed, so a new insert is needed when installing a new retainer.
68
OPTIONAL RETAINERS
Retainer Part Number
5135077
(standard on M-10 128)
5134923
5135080
(standard on M-10 136)
Preload
Least
Middle Middle
Most
Sag
Most
Least